Multiple pole vacuum switch



y 1959 L. B. sTEwAlD ET AL 2,886,668

MULTIPLE POLE VACUUM SWITCH Filed Aug. 6, 1956 ///\/E/vT0/?s LEW/S 5. STEWARO JACK s. HAWK/NS tbe/r ATTORNEY United States Patent MULTIPLE POLE VACUUM SWITCH Lewis B. Steward, San Jose, and Jack '5. Hawkins, Campbell, Calif., assignors to Jennings Radio Manufacturing Eorporafion, San Jose, Calif a corporation of Caliorma Application August 6, 1956, Serial No. 602,247

11 Claims. (Cl. 200-104) Our invention relates to vacuum switches, particularly of the multiple pole type.

One of the principal objects of our invention is the provision of a multiple pole vacuum switch having a substantially perfect reliability within the range of capacity, power and operative life for which it is designed.

Other objects of our invention include the provision of a multiple pole vacuum switch capable of withstanding without impairment in operation, the most violent acceleration and shock and high temperature; having very low contact resistance; having a self-contained actuator with low power requirements; and characterized by extremely low inductance; small compact size; extremely rugged construction, and adaptability for mass production at low cost.

There are many other objects of our invention which will be brought out in the following description. We do not limit ourselves to the showing made by said description and the drawings, since we may use variant forms of the invention within the scope of the appended claims.

The development of guided missiles has required a switch having the characteristics above referred to. Most of these newly designed pieces of equipment require a vacuum switch of multiple pole type to handle a multi plicity of operations. Generally, the voltages are low, and the currents also are in low range. However to insure absolutely reliable as well as efiicient operation, we have designed our switch for high current carrying capacity as compared to voltage breakdown. In the switch illustrated, we assume these voltages never to exceed 1000 and the test voltages on the pumps never to exceed 1500.

Structurally, the vacuumized envelope of our switch is formed by brazing together an assembly of annular pieces or rings of metallized ceramic material, alternating with thin flat feed and contact rings, a common feed ring lying between two contact rings; and thus controlling twocircuits. In the drawings, Fig. 1 shows four common feed rings and eight separate controlled circuits. The lateral cylindrical wall thus formed by the rings is closed at its opposite ends with metallic plate structures; one of which provides a mounting for a metallic tubulation, and the other of which provides a mounting for the operator mechanism, part of which is within the envelope and part outside of it.

An important feature of our invention lies in our assembly and sealing of components, the easily accessible interior surfaces of which have previously been cleaned, so that the closed assembly does not require the difiicult washing to remove oxides and contamination which has heretofore been necessary in the manufacture of vacuumized envelopes housing electrical devices.

By our method of construction, the extremely simple component parts lend themselves to rapid assembly and brazing together to form an hermetically tight envelope, ready for evacuation and final high heating.

Another important feature of our invention lies in the use of molybdenum for the thin feed and contact rings. This metal has natural properties of which we make con- 2 structive use in forming the parts and giving them the desired qualities in the finished product.

The contacts are machined from annealed molybdenum and after all machine work is completed, the parts are vacuum fired at a temperature far above the melting temperature of the silver solder used to braze the unit together. During this vacuum firing the metal undergoes a molecular change and becomes hard and resilient or spring-like. After vacuum firing, the parts are brazed together, and after final assembly, the envelope is evacuated and heated to a temperature somewhat below the melting temperature of the silver solder. The brazing temperature and the bake out temperature have little or no infiuence on the spring characteristics of the molybdenum.

Referring now to the drawings which are one and one half times actual size:

Fig. l is a vertical half sectional view of our multiple switch, the plane of section being indicated by the line 11 of Fig. 2.

Fig. 2 is a plan view of our switch.

Fig. 3 is a horizontal sectional view of our switch taken in the plane indicated by the line 3--3 of Fig. 1. A portion of the mounting flange 42 is omitted. The view shows the common feed plate 3 in plan.

Fig. 4 is a plan view of one of the contact plates.

In the main body of our switch we use ceramic rings 2 which have been metalized on both flat faces, alternated with molybdenum rings 3 and 4 until the required length of the cylindrical assembly is attained. The rings 3 are each formed with preferably three internally extendingspokes 6, which extend almost to the center of the ring. The ends of the spokes mechanically engage in an annular groove 7 formed between the sections of the central ceramic stem 9, extending upwardly from the armature plate 12, and held in rigid assembly thereon by the tie rod 13 and nut 14.

Each of the rings 3 is thus mechanically connected to the insulated stem by the spokes or arms 6 which thus position and support the stern and armature in the envelope. Since the arms are molybdenum and have been treated to make them spring-like, such support is resilient, and the stem and all of the spokes (three for each ring 3) respond to induced movements, up and down, of the armature 12'. Each set of spokes, however is insulated by the ceramic stem from all the others.

Each of the rings 3 is also provided with an outwardly extending terminal lug 15, serving as an outside terminal for connecting the ring and its three spokes into a circuit.

In the double throw switch shown in Fig. 1, we provide for the control of two circuits by the reciprocation of each set of spokes, using each ring 3 with its lug 15 as a common feed for the two circuits. In order to do this, we assemble a molybdenum contactc ring 4 on each side of each common feed ring 3. Each contact ring 4 is formed with inwardly extending arms 17, each terminating in a curved contact finger 18. These arms and fingers are also resilient.

In the assembly as shown in Fig. I, the fingers 18 are turned toward the associated common feed ring spokes 6, and end with a carefully assigned spacing between them. There is thus a set of three contact fingers on each side of each set of three common feed spokes; and the spacing and arrangement is such that with each full movement of the stem in either direction, three separate resilient contact fingers on an associated ring 4 are firmly pressed by the three spokes 6 of the associated feed ring. Thus with the assembly shown which includes four common feed rings 3, four circuits may be closed by movement of the stem upwardly; and these broken and four others closed by movement of the stern downwardly. In each case, each circuit is closed by three separately operating contacts.

--The-engagement of each spoke with its associatedfinger is direct Without lateral sliding and under resiliently 'applied pressure; and may be readily assumed to be suf- 'fiei'ent to insure proper closing of a circuit and to ofier very little resistance. However, to make closing of a g'i've'n"circuit-absolutely certain, the three points of direct '-contact in parallel are arranged; and in a rugged vacuu'miz'ed envelope, "so that there is substantially no chance of failure because of imperfect engagement or fouled contaet' points.

Each' of the molybdenum rings 4 is also provided with 'a terminal lug 19 by which it is connected in circuit; and the angular spacing of lugs and spokes or arms is such that in assembly, the spokes'and arms are axially or vertically aligned While the lugs are spaced at angular intervals compelled or preferred for convenient connection "into the many circuits served.

The upper end of the switch is hermetically closed by a metal top plate 21 integrally united as by brazing to the mp-most ceramic ring; and a metal tube 22 provides rugged means for sealing off the envelope after the exhausting procedure.

Brazed to the lower face of the bottom ceramic ring is-a copper ring or-a-nn'ulus '24, having-an externalflange "'26 This entire ring assembly of top plate, tubulation alternated ceramic and metal rings, and flanged annulus, together withthe central stem and armature, is put together and then brazed in the furnace in one operation.

Brazed to and axially aligned with the ring assembly is 'a'steelhousing 28 containing the actuating elements -of*our"switch The housing has a transverse partition '29 brazed to and hermetically closing the housingnear its nr'end'butleavingits'free end outsidethe' vacuumized part of theenvelo'pe. Mounted rigidly in the partition and integrally united thereto is the electro-magnetic core '31,'it's inner-"end widened into the head 32, just'below and 'spaced from'the armature 12. Between the partition '-and the armature 'is the 'spiral spring 33 which normally presses the armature and stem upwardly to close 'the upper "series of contacts. The upper contacts are "broken 'and'the lower contactsclosed, when'the armature and stem are drawn do'wnyand this occurs when the-coil "34' surrounding the core is energized.

The coil is mounted on a base plate .36, held on the l'owerendof the housing 28 by a single screw 37 threaded into the end of-the core. Leads 38'for the windings on the coil pass through the plate in sealed-bushings 39. Coils are thus quickly removed and replaced, 'or exchanged for-others of different electrical values.

I *B'efore joiningthe housing 23 to the ring assembly we first braze an annular channel 41 to the rim of the housing'alongwitha mounting flange'42, and then assemble the spring '33 around the head end of the core. This unit is "then: placed within the 'seat formed by the flanged ring 24- 26, and brazed by heliarc, so that the heat of brazing -is localized "andexcessive heat is not transmitted to other "parts within theenv'el'ope.

-This helia'rc'brazing is done with a mixture of nitrogen and hydrogen inside the envelope at slightly above atmospheric pressure, so that formation of oxides therein "-during" the brazing is prevented, and the cleanliness of the is fully preserved. For this forming gas mixture, we 'use about 85% nitrogen-and 15% hydrogen. Immediatefly'aftefthe heliar'c brazing'the switch envelope is ready -for exhaustion and 'final flake-out heating.

Thefparticular design shown is intended for direct-curtlow voltage usage. Due to'small size and high efli- 1 'elene'y, theactu'ating' Wattage is kept low andis predicated on the aiiiount of-dampening and internal friction desired i-t'o inake the switchwithstand the required vibration and s ock tests. It is obvious however that by expanding the size ofthe rings'we'c'an'make a high voltage, heavy duty using thesame'basictechnique to eliminate much ef the "costly hand work formerly required in producing vacuumized switches.

-0ur-swi-teh-is particularly suitable for ---radio frequency service since inductance has'been kept at a minimum, and no external mechanism isrequired for operation. No matter to what type of service our switch is to be applied, the coil assembly can be operated at ground potential without danger of fiashing -o'verinternally due to insuflicient resistance to ground. I

It will be obvious without specific illustration or description that our invention may be embodied in a switch having any desired number of poles,'either single or double throw, by a suitable number of ceramic rings alternated with common feed rings 3 and contact rings 4, arranged as necessary to give the desired single or double throw operation.

We claim:

1. A vacuumized switch comprising a plurality of metallized ceramic rings, metal rings interposed between the ceramic 'ri'ngs and -bra'zed thereto to unitall the rings in an hermetically tight assembly, an 'end' plate structure clos- "ing each opposite end of the-ring assembly, contact finge'r's arranged "on selected 'metal rings, support arms ar- "rangedon adjacent metal rings, 'a 'stem within the ring assembly'and mounted 'in the'support arms, and means for-moving the stem to make and'b'reak electrical contact betweenthe support'arrn's' and the contact fingers.

2. A vacuumized 'switch in accordance with claim 1,

'"in which the stem is insulated from the support arms and terminates "at one end in an armature adjacent an end plate' 'st'ructurm and spring means are arranged within the 'ringfassembly and a'magnetic coil-outside the ring assem- '-bly and adjacent thea'r'mature to reciprocate the stem.

3. A multiple pole vacuum switch comprising an 'assembly of alternate rings of metallized ceramic and metal brazed together, each'of the metal rings having an ex- "ternally 'extendingterminal lug 'and apluralityof inter- -nally extending arms, a metal plate brazed to and closing one end'of the ring assembly, a housing having an integrally unitedpartition extending thereacross and'brazed to ajndclo'sing theopposite end of the ring assembly and providiii'g a vacuumized housing portionand a free end portion, a dielectric stem axially arranged Within the ring assembly and mechanically connected to the arms of selected rings, contact fingers arranged on the arms of each ring nextadjacent aselected ring, and means within the housing for moving the stem to engage and disengage the "arms {of 'a-said selected 'ring and the fingers of the adjacent ring.

4. A switch in accordance with claim 3 in which con- "tact'finge'rs are arranged on the arms of a ring on each side of each selected ring.

' 5. A switch in accordance with claim 4 in which the stem is moved in one direction by'a spring within the vacuumized portion of the housing and moved-in the other direction by a magnetic coil within the housing and outside the partition.

6. A 'switch in accordance with claim 5 in which the "free end of the housing is provided with a'removable cover plateon which anelectric coil is mounted.

7. A switch-in accordance with claim 6 in which the coil surrounds acore extending through and integrally united with the partition. I

8. ;A switch in accordance withclaim 7 in which the stem' is provided with-an armature "close to the inner-end or the-core and the spring is interposed between the armature and the'p artition. p

9. 'va'cinn'h'iied envelope for 'an electric switch comprising an assembly'of alternate rings of'metallizedceramic and metal'brazed'together, a plateclosin'g oneend of theasseinb ly, a flanged base ring brazed to the open other end "of the assembly, "an annular channel brazed within the flange of the base ring, and a housing having a transverse'partition and brazed within the channel to close the envelope, said partition defining a vacuumized housing-portion and a free end portion.

10. -1A'vaeuumswitchin accordance with claim 9 in which fixed and movable contact portions are arranged on the metal rings inside the envelope and terminal lugs are arranged on the metal rings outside the envelope, and means for moving the movable contact portions include spring means on the vacuum side of the housing partition and a magnetic coil on the opposite side.

11. A vacuumized switch comprising an assembly of dielectric rings having oppositely disposed metallized faces, conductive rings interposed between adjacent dielectric rings and hermetically joined thereto, means her- 10 metically joined to the end dielectric rings and closing the opposite ends of the ring assembly, a fixed contact arranged on a selective conductive ring, a resilient arm arranged on an adjacent conductive ring, and means 6 mounted on the ring assembly to move the resilient arm into and out of engagement with the fixed contact.

References Cited in the file of this patent UNITED STATES PATENTS 1,575,599 Hornberger Mar. 2, 1926 2,150,379 Kerschbaum Mar. 14, 1939 2,234,834 Scott Mar. 11, 1941 2,339,675 Bucklen et al Jan. 18, 1944 2,460,201 Trump et a1 J an. 25, 1949 2,514,913 Tyrner July 11, 1950 2,775,671 Dreyfus Dec. 25, 1956 

